We usually regard trees as natural umbrellas. A large fir tree is the best place to hide from a rain, because it catches up to 50% of water falling from the sky. But you’d better forget about it in industrial areas. Rains there are dirty, and become even dirtier, when they permeate tree crown. Such a conclusion was made by V.V. Nikonov and N.V. Lukina, research fellows of RAS Colsky Science Centre Institute of Industrial Ecology Problems.
 

The scientists have studied precipitation composition and acidity in coniferous forests of Cola Peninsula, where the large copper-nickel plant “Severonikel” is located, for the period of 1991 to 1997. This plant is one of the most powerful sources of atmosphere industrial contamination in Northern Europe. This plant is the reason why acid rains water most northern coniferous forests and dust, containing heavy metals, spreads everywhere and settles on the tree crowns.
 

Rainwater usually changes its composition while flowing through tree crown. Water washes dust, insect excrements and plant effusions from tree crown and washes out different elements (carbon, calcium and manganese, for example). Thus, under a fir tree precipitations are more acid and rich in many elements than between the trees. Element content may differ tenfold. In pine forests such tendency is not so clearly defined.
 

If the rains are acid, which is common in forests surrounding industrial zones, they eat tree needles and wash out more calcium, magnesium and manganese. The result is that rains penetrated fir tree crowns become more acid, and copper and nickel concentrations increase 50-100fold. So plants and soil under the fir trees suffer much more contamination than between the trees. That is why the scientists have found most serious contaminations under the trees, especially under the fir trees. The same reason is why trees tend to die, and forests turn to open woodlands.
 

It’s not always raining over northern coniferous forests. From 100 to 200 days the trees are covered with snow, which too concentrates all atmospheric contaminations, but it is mainly rain that influences forest’s health.
 

Seems interesting that ecologists, while performing research on atmospheric loads on northern forests, usually study only open forest spaces. V.V. Nikonov and N.V. Lukina think that such estimation is undervalued, and it is necessary to study contamination under the trees.